Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$186.35	4.473%	$194.6854	$194.69	$194.70	$194.70
Purchase #2	$109.43	7.191%	$117.2991	$117.30	$117.30	$117.30
Purchase #3	$202.92	7.489%	$218.1167	$218.12	$218.10	$218.10
Purchase #4	$31.40	7.749%	$33.8332	$33.83	$33.85	$33.80
Purchase #5	$52.31	13.776%	$59.5162	$59.52	$59.50	$59.50
Purchase #6	$152.88	7.587%	$164.479	$164.48	$164.50	$164.50
Purchase #7	$116.56	8.320%	$126.2578	$126.26	$126.25	$126.30
7 purchase totals =	$851.85		$914.1874	$914.20	$914.20	$914.20